Shape lockable apparatus and method for advancing an instrument through unsupported anatomy

ABSTRACT

Apparatus and methods are provided for placing and advancing a diagnostic or therapeutic instrument in a hollow body organ of a tortuous or unsupported anatomy, comprising a handle, an overtube disposed within a hydrophilic sheath or liner, and a distal region having an atraumatic tip. The sheath/liner may be disposable to permit reuse of the overtube. Loading devices may be provided for disposing the sheath/liner about the overtube. Tensioning mechanisms may be provided to selectively stiffen the overtube to reduce distension of the organ caused by advancement of the diagnostic or therapeutic instrument. The distal region permits passive steering of the overtube caused by deflection of the diagnostic or therapeutic instrument, while the atraumatic tip prevents the wall of the organ from becoming caught or pinched during manipulation of the diagnostic or therapeutic instrument.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a non-provisional of U.S. Patent ApplicationSer. No. 60/570,111, filed May 10, 2004, the full disclosure of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to apparatus and methods for placing andadvancing a diagnostic or therapeutic instrument in a hollow body organof unsupported anatomy, while reducing patient discomfort and risk ofinjury.

The use of the colonoscope for examining the interior of the largeintestine or colon is well-known. In general, a physician performing anexamination or treatment of the colon inserts a colonoscope into theanus and then advances the colonoscope into the colon. A completeexamination requires the physician to advance the colonoscope into thecolon, negotiate the sigmoid colon, and left and right colic flexures upto the cecum. Advancement of the colonoscope is generally accomplishedby manipulation of a steerable tip of the colonoscope, which iscontrolled at the proximal end of the device by the physician, inaddition to torqueing and pushing the scope forward or pulling itbackward.

Problems regularly occur, however, when negotiating the colonoscopethrough the bends of the colon, such as at the sigmoid and left andright colic flexures. These problems arise because the colon is soft andhas unpredictable fixation points to the viscera of the abdomen, and itis easily distensible. Consequently, after the steerable tip of thecolonoscope is deflected to enter a new region of the colon, theprincipal direction of the force applied by the physician urging theproximal end of the device into the patient's colon is not in thedirection of the steerable tip. Instead, the force is directed along theaxis of the colonoscope towards the preceding bend(s), and causesyielding or displacement of the colon wall.

[The loads imposed by the colonoscope on the colon wall can have amyriad of possible effects, ranging from patient discomfort to spasticcramp-like contractions of the colon and even possible perforation ordissection of the colon. Consequently, the colonoscope cannot beadvanced as far as the cecum in up to one-sixth of all cases.

To address some of these difficulties, it is known to employ a guidetube that permits a colonoscope to be advanced through the rectum. Onesuch device is described in U.S. Pat. No. 5,779,624 to Chang. Analternative approach calls for inserting the colonoscope through acurved region, and then mechanically actuating the portion of the devicein the curved region to cause it to straighten, as described in U.S.Pat. No. 4,601,283 to Chikama.

Many patients find the operation of such previously-known devicesunpleasant because the sigmoid portion of the colon is forced into analmost rectilinear shape by the guide tube. Due to the stiffness of theguide tube, careless handling of the guide tube presents a risk ofinjury to the colon.

Other previously-known apparatus and methods use an overtube havingvariable rigidity, so that the overtube may be inserted through curvedanatomy in a flexible state, and then selectively stiffened to resistbending forces generated by passing a colonoscope through the overtube.One example of such a device is described in U.S. Pat. No. 5,337,733 toBauerfiend. The device described in that patent comprises inner andouter walls having opposing ribs spaced apart across an air-filledannulus. The ribs are selectively drawn together to intermesh, and forma rigid structure by evacuating the annulus.

Another previously-known endoscopic device for delivering aneurysm clipswithin a hollow organ or vessel is described in U.S. Pat. No. 5,174,276to Crockard. The device described in that patent includes a conduitformed from a multiplicity of elements that are capable of angulationrelative to one another, and which becomes rigid when subjected to atensile force. The device is described as being particularly useful inneurosurgery, where the variable rigidity of the device is useful forproviding a stable platform for neurosurgical interventions, such asclipping an aneurysm.

While previously-known apparatus and methods provide some suggestionsfor solving the difficulties encountered in advancing diagnostic ortherapeutic instruments through easily distensible body organs, fewdevices are commercially available. Although the precise reasons forthis lack of success are uncertain, previously-known devices appear topose several problems.

For example, the devices described in the Bauerfiend and Crockardpatents appear to pose a risk of capturing or pinching tissue betweenthe endoscope/colonoscope and the distal end of the overtube or conduitwhen the scope is translated. Also, neither device provides any degreeof steerability, and must be advanced along the pre-positioned scope. Inaddition, the bulk of the proximal tensioning system described inCrockard is expected to interfere with manipulation of the endoscope.Other drawbacks of previously-known devices may be related to thecomplexity or cost of such devices or the lack of suitable materials. Inany event, there exists an un-met need for devices to solve thislong-felt problem in the field of endoscopy and colonoscopy.

In view of the foregoing, it would be desirable to provide apparatus andmethods for facilitating placement of diagnostic or therapeuticinstruments within easily distensible hollow body organs, such as theesophagus or colon.

It further would be desirable to provide apparatus and methods thatpermit a diagnostic or therapeutic device to be advanced into a hollowbody organ, and which facilitates passage of the device through tortuousanatomy without requiring straightening of organ passageways alreadytraversed.

It also would be desirable to provide apparatus and methods forfacilitating placement of diagnostic or therapeutic instruments withineasily distensible hollow body organs that include means for reducingthe risk that tissue will become inadvertently pinched between theapparatus and the advancing or withdrawing instrument, or caught as thediagnostic or therapeutic instrument is maneuvered through the hollowbody organ.

It still further would be desirable to provide apparatus and methodsthat provide a low-cost, single use, easily manufacturable guide forinserting a diagnostic or therapeutic instrument in a hollow body organ.

It yet further would be desirable to provide apparatus and methods thatprovide a low-cost, easily manufacturable guide for inserting adiagnostic or therapeutic instrument in a hollow body organ, wherein aportion of the apparatus is disposable after a single use and aremaining portion of the device is re-usable.

Still further, it would be desirable to provide a device having aselectively locking shape for inserting a diagnostic or therapeuticinstrument in a hollow body organ, but which facilitates manipulation ofa proximal end of the diagnostic or therapeutic instrument.

It additionally would be desirable to permit multiple diagnostic ortherapeutic devices to be positioned in a hollow, unsupported organ, sothat at least one of the devices may be withdrawn and repositioned whilethe other devices are retained in place.

It further would be desirable to provide apparatus and methods forfacilitating placement of diagnostic or therapeutic instruments withineasily distensible hollow body organs that reduces the risk ofreconfiguration of the apparatus in the event of failure of the device.

It yet further would be desirable to provide apparatus and methods forfacilitating placement of diagnostic or therapeutic instruments withineasily distensible hollow body organs that substantially maintains anaxial length of the apparatus.

BRIEF SUMMARY OF THE INVENTION

Apparatus is provided comprising a proximal handle, an overtube coupledto the proximal handle and having a distal region, an atraumatic tipdisposed on the distal region, and mechanisms for selectively lockingthe shape of the overtube to assist one or more diagnostic ortherapeutic instruments to negotiate the tortuous or unsupported anatomyof a hollow body organ, rather than distending the wall of the organ.The apparatus includes a main lumen extending between the handle,overtube and atraumatic tip, through which a diagnostic or therapeuticinstrument, such as an endoscope or colonoscope, may be translated.

The handle extends from the patient, e.g., through the mouth or anus,where it can be manipulated by the physician. The proximal handle mayform part of a single use, disposable apparatus, or may be separablefrom the overtube and reusable. Alternatively, the overtube may includea disposable single-use cover that fits over a reusable structure. Theovertube may be angled relative to a working axis of the handle, so thatthe handle does not interfere with manipulation of the diagnostic ortherapeutic instrument inserted through the overtube.

The overtube may comprise a multiplicity of nested elements that areselectively-tensionable by actuation of a ratchet, a pneumaticmechanism, or shape memory materials. Alternatively, the overtube mayinclude a series of interconnected links surrounded by a selectivelyactuable clamping mechanism, a tubular member comprising a multiplicityof helical links formed from a material having variable durometer andsurrounded by a clamping mechanism, a thermo-responsive polymer oralloy, an elongate, flexible tube made from an electroactive polymer, ora series of overlapping or nested links that are made from a shapememory material. The overtube may include any of a number of aids forfacilitating passage of the diagnostic or therapeutic instrument throughthe main lumen, including a lubricious liner, rails or rollers.

The tensioning systems may provide a fail-safe mode that reduces therisk of reconfiguration of the overtube in the event that the mechanismfails. The fail-safe mode may equalize compressive clamping loadsapplied to the overtube when the overtube is rigidized, and beconfigured to rigidize the overtube without substantial proximalmovement of the distal region.

The liner may be made from thin, flexible material, have a hydrophiliccoating, incorporate a kink-resistant coil, or combinations thereof.Alternatively or additionally, the liner may comprise a disposablesheath that may be removed from the overtube to permit re-use of theinternal structure of the overtube. Apparatus and methods for disposingthe liner within the main lumen of the overtube are provided.

The atraumatic tip of the present invention preferably is configured toreduce the risk of capturing or pinching tissue between the overtube anda diagnostic or therapeutic instrument that is selectively translatedthrough the overtube. This is preferably accomplished by the atraumatictip applying a radially-outwardly directed load to the wall of thehollow body organ in the vicinity of the distal region where thediagnostic or therapeutic instrument exits the apparatus.

In addition, the distal region of the overtube preferably includes aflexible portion that permits a steerable tip of a diagnostic ortherapeutic device disposed within the distal region to deflect thedistal region of the overtube in a desired direction. This permits theovertube to be readily advanced together with the steerable tip of thediagnostic or therapeutic device.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features of the invention, its nature and various advantageswill be more apparent from the accompanying drawings and the followingdetailed description of the preferred embodiments, in which:

FIG. 1 is a schematic view of a human colon illustrating a commondifficulty encountered in advancing a colonoscope beyond the sigmoidcolon;

FIG. 2 is a side view of illustrative apparatus of the presentinvention;

FIG. 3A is a side-sectional exploded view of nestable elements of afirst embodiment of an overtube suitable for use in the apparatus ofFIG. 2;

FIG. 3B is a side view of two of the nestable elements of FIG. 3A nestedtogether;

FIG. 4 is a side-sectional view of a distal region of the apparatus ofFIG. 2 constructed in accordance with principles of the presentinvention;

FIG. 5 is a side-sectional view of an illustrative arrangement of amechanism suitable for use in the handle of the apparatus of FIG. 2;

FIG. 6 is a side-sectional view of the detail of a wire clamping systemsuitable for use in the handle of FIG. 5;

FIG. 7A-7C are schematic views of a method of using the apparatus of thepresent invention;

FIG. 8 is a schematic view of an alternative step in the method of usingthe apparatus of the present invention;

FIG. 9 is a side view of an alternative embodiment of the apparatus ofthe present invention;

FIGS. 10A-10C are schematic views of components of a tensioningmechanism suitable for rigidizing the overtube of the present invention,wherein the components provide a fail-safe mode;

FIG. 11 is a cut-away side view of a tensioning mechanism incorporatingthe components of FIGS. 10A and 10B within the handle of the apparatusof FIG. 2;

FIGS. 12A-12D are schematic perspective views of alternative componentsof a tensioning mechanism that each provide a fail-safe mode;

FIGS. 13A and 13B are, respectively, a side sectional view of atensioning mechanism incorporating the pulley manifold of FIG. 12Bwithin the handle of the apparatus of FIG. 2, and an indicator thatdisplays the status of the overtube;

FIGS. 14A-14C are cut-away side views of an alternative tensioningmechanism that transitions the overtube of the present invention betweenflexible and rigid states with successive actuations;

FIG. 15 is a side sectional view of yet another alternative tensioningmechanism employing pneumatic actuation;

FIG. 16 is a side sectional view of a further alternative tensioningsystem that transitions the overtube of the present invention from aflexible state to a rigid state without substantial movement of a distalend of the overtube;

FIGS. 17A and 17B, respectively, are a side-section view of analternative element suitable for use in the overtube of FIG. 2 and aroller element suitable for use with the element of FIG. 17A,respectively;

FIGS. 18A and 18B depict the use of lubricious rails in the overtube ofthe apparatus of FIG. 2 or 9 to facilitate passage of a diagnostic ortherapeutic device through the main lumen;

FIG. 19 is a side-sectional view of an alternative nestable elementhaving an integral lubricious lining;

FIGS. 20A and 20B are side-sectional views of alternative nestableelements that form a smooth internal lumen when nested together;

FIGS. 21A-21D are still further alternative embodiments of the nestableelements of FIG. 3, in which the nestable elements are macroscopicallytextured to enhance friction;

FIG. 22 is a schematic view of the lumen of the overtube of the presentinvention depicting the use of multiple devices;

FIGS. 23-28 depict side-sectional views of various alternativeembodiments of an atraumatic tip constructed in accordance with thepresent invention;

FIGS. 29 and 30 are alternative embodiments of the overtube of thepresent invention, having tensioning systems that employ shape memorymaterials;

FIGS. 31A-31C are, respectively, a side-sectional view of an alternativeembodiment of an overtube suitable for use in the present inventionhaving a multiplicity of interconnected links surrounded by a clampingsleeve, and cross-sectional views of portions of the sleeve;

FIG. 32 is a side-sectional view of a further alternative embodiment ofan overtube constructed in accordance with the present invention havinga spiral bladder to actuate the clamping links;

FIG. 33 is a side-sectional view of another alternative embodiment of anovertube of the present invention having thermally-actuable bands;

FIGS. 34A and 34B are side-sectional views of a yet further alternativeembodiment of an overtube of the present invention comprising a seriesof helical links having regions of different durometer;

FIG. 35 is a side-sectional view of a still further alternativeembodiment of an overtube suitable for use with the present inventioncomprising a series of links having proximal and distal rims thatinterlock;

FIG. 36 is a side-sectional view of another alternative embodiment ofthe present invention comprising a series of links that form coactingjoints;

FIG. 37 is a side-sectional view of yet another alternative embodimentof an overtube having thermally regulated stiffness;

FIGS. 38A-38C are schematic views of yet another alternative embodimentof an overtube suitable for use with the present invention, in which thediameters of tension wire lumens extending through the overtube varyresponsive to electrical energization;

FIG. 39 is a side-sectional view of still another alternative embodimentof an overtube having a series of electrically activated links disposedin an overlapping fashion around a series of rigid links;

FIGS. 40A and 40B are side-sectional views of, respectively, anelectrically activated nestable link and a plurality of the electricallyactivated nestable link of FIG. 40A nested together to form an overtubesuitable for use with the apparatus of the present invention;

FIG. 41 is a side-sectional view of a disposable sheath for use with theovertube of the present invention;

FIG. 42 is a schematic side view of a strap that couples the apparatusof the present invention to a colonoscope;

FIGS. 43A-43C are, respectively, isometric, top and side views of aloading device for inserting a liner within apparatus of the presentinvention;

FIGS. 44A-44C are, respectively, isometric, top and side views of analternative loading device, liner and apparatus handle of the presentinvention;

FIGS. 45A-45C are, respectively, isometric, top and side views of theapparatus of FIG. 44, illustrating a method of detaching the loadingdevice from the liner;

FIGS. 46A and 46B are top and side views of the apparatus of FIGS. 44and 45, illustrating a method of securing the liner to the apparatushandle; and

FIGS. 47A and 47B are top and side views of a variation of the apparatusof FIG. 46 comprising a fluid reservoir.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, problems associated with previously-known apparatusand methods for inserting and advancing a diagnostic or therapeuticinstrument into a hollow body organ having tortuous or unsupportedanatomy, illustratively, patient's colon C, are described. Colon Cincludes sphincter muscle SM disposed between anus A and rectum R.Rectum R is coupled via the rectosigmoid junction RJ to sigmoid colonSC. Sigmoid colon SC joins descending colon DC, which in turn is coupledto transverse colon TC via left colic flexure LCF. Transverse colon TCalso is coupled by right colic flexure RCF to ascending colon AC andcecum CE, which receives waste products from the small intestine.

As illustrated in FIG. 1, colonoscope 10 having steerable distal tip 11is typically inserted through anus A into rectum R, and then steeredthrough rectosigmoid junction RJ into sigmoid colon SC. As depicted inFIG. 1, distal tip 11 of colonoscope 10 is advanced through sigmoidcolon SC and deflected into descending colon DC. Further urging of thecolonoscope by the physician can cause region 12 of the colonoscope tobear against and cause displacement of the rectosigmoid junction RJ, asillustrated by dotted lines 12′ and RJ′ in FIG. 1.

Such distension may result in patient discomfort or spasm, and ifunnoticed, could result in injury to the colon. The potential formovement of colonoscope to cause distension, discomfort or spasm is alsogreat where the colonoscope must negotiate left colic flexure LCF andright colic flexure RCF, and results in a large portion of suchexaminations terminating before the physician can advance distal tip 11to cecum CE.

The present invention provides apparatus and methods for placing adiagnostic or therapeutic instrument through the tortuous orunpredictably supported anatomy of a hollow body organ, such as theesophagus or colon, while reducing the risk of distending or injuringthe organ. Apparatus constructed in accordance with the presentinvention permits an endoscope or colonoscope to be readily advancedinto a patient's tortuous or unsupported anatomy by selectivelyshape-fixing an overtube portion of the apparatus, while also preventingtissue from being captured or pinched between the overtube and scope.

Referring now to FIG. 2, apparatus 20 of the present invention isdescribed. Apparatus 20 comprises handle 21, overtube 22, and distalregion 23 having atraumatic tip 24. Handle 21 includes lumen 25 thatextends from Toughy-Borst valve 26 through overtube 22, distal region 23and atraumatic tip 24. Lumen 25 is configured to facilitate passage of astandard commercially available colonoscope, such as colonoscope 10,therethrough. Toughy-Borst valve 26 may be actuated to releasably lockcolonoscope 10 to apparatus 20 when colonoscope 10 is inserted withinlumen 25. As described hereinafter, overtube 22 is configured so that itcan be selectively transitioned between a flexible state and a rigid,shape-fixed state by actuator 27 disposed on handle 21.

In FIG. 3A, illustrative embodiment of overtube 22 comprises amultiplicity of nestable elements 30. For purposes of illustration,nestable elements 30 are shown spaced-apart, but it should be understoodthat elements 30 are disposed so that distal surface 31 of one element30 coacts with proximal surface 32 of an adjacent element. Each ofnestable elements 30 has central bore 33 to accommodate colonoscope 10,and preferably two or more tension wire bores 35. When assembled asshown in FIG. 2, nestable elements 30 are fastened with distal andproximal surfaces 31 and 32 disposed in a coacting fashion by aplurality of tension wires 36 that extend through tension wire lumens 28defined by tension wire bores 35. Tension wires 36 preferably are madefrom a superelastic material, e.g., nickel titanium alloy, to provideflexibility, kink-resistance and smooth movement of the tension wiresthrough tension wire bores 35. Alternatively, the tension wires may bemade from braided stainless steel, a single stainless steel wire,Kevlar, a high tensile strength monofilament thread, or combinationsthereof. These materials are provided only for the sake of illustrationand should in no way be construed as limiting.

In a preferred embodiment, a ratio of the diameter of tension wires 36to the diameter of tension wire bores 35 approximately is in a range of½ to ⅔. Applicants have observed that this provides smooth relativemovement between the tension wires and the nestable elements, even whenovertube 22 is retroflexed. While a greater ratio is desirable, such aconfiguration appears to cause the edges of tension wire bores 35 togouge into tension wires 36, thereby constraining movement of thetension wires through the tension wire bores. Conversely, whileapplicants contemplate that a smaller ratio would provide even smootherrelative movement, the resultant increase in the thickness of wall 34 ofeach nestable element 30 is undesirable.

In a preferred embodiment, adjacent surfaces 31 and 32 of each nestableelement 30 are contoured to mate with the next adjacent element, so thatwhen tension wires 33 are relaxed, surfaces 31 and 32 can rotaterelative to one another. Tension wires 36 are fixedly connected to thedistal end of overtube 22 at the distal ends and to a tensioningmechanism disposed within handle 21 at the proximal ends. When actuatedby actuator 27, tension wires 36 impose a load that clamps distal andproximal surfaces 31 and 32 of nestable elements 30 together at thecurrent relative orientation, thereby fixing the shape of overtube 22.

When the load in tension wires 36 is released, tension wires 36 providesfor relative angular movement between nestable elements 30. This in turnrenders overtube 22 sufficiently flexible to negotiate a tortuous paththrough the colon. When the tensioning mechanism is actuated, however,tension wires 36 are retracted proximally to apply a clamping load tothe nestable elements. This load prevents further relative movementbetween adjacent elements 30, and stiffens overtube 22 so that anydistally directed force applied to colonoscope 10 causes distal tip 11to advance further into the colon, rather than cause overtube 22 to bearagainst the wall of the colon. The shape-fixed overtube absorbs anddistributes vector forces, shielding the colon wall.

In a preferred embodiment, the radius of curvature of proximal surface32 closely approximates the radius of curvature of distal surface 31. Inparticular, a ratio of the radius of curvature of distal surface 31 tothat of proximal surface 32 is in an approximate range of about 0.9 to1.0. Furthermore, the coefficient of static friction between the distaland proximal surfaces preferably is in an approximate range of 0.2 to1.4 (based on ASTM standard D1894). This structure appears to permitsufficient frictional force to develop between the surfaces to preventrelative movement between adjacent elements when overtube 22 isrigidized.

Nestable elements 30 may be configured to provide a stack-up of overtube22 that is a function of the growth height. As defined in FIG. 3B,growth height H is the increase in the longitudinal length of overtube22 when one nestable element 30 is nested within another nestableelement 30. To accommodate the radius of curvature obtainable bystandard commercially available colonoscopes, growth height H preferablyis less than or equal to about 0.31 in, and more preferably about 0.16in. This provides overtube 22 with sufficient flexibility to assume aradius of curvature that is less than or equal to approximately 0.95 in.If overtube 22 needs to accommodate other endoscopes or medicalinstruments that are larger or smaller in size and/or that may assumedifferent radii of curvature, or the overtube needs to accommodatetighter anatomical constraints, applicants contemplate that growthheight H may be increased or decreased proportionate to the change indimensions of overtube 22. Applicants note that the precedinggeometrical characterization of nestable element 30 does not account formaterial interference or effects to the tension wire bores, which areomitted from FIG. 3B for illustrative purposes.

Nestable elements 30 preferably are molded from a polymer filled withfibers of glass, carbon, or combinations thereof. In a particularlyuseful embodiment, nestable elements 30 are molded from polyurethanefilled with 20-40% by volume of glass fibers, 20-40% by volume of carbonfibers, or 20-40% by volume of glass and carbon fibers. One example isisoplast 2540, which is available from Dow Chemicals, Midland, Mich.Applicants have observed that such materials enhance friction betweenadjacent elements, which advantageously reduces the risk of relativeangular movement between the adjacent elements when overtube 22 isstiffened and, thus, reduces the risk of undesired reconfiguration ofovertube 22 in its shape-locked state. While a greater amount of glassand/or carbon fibers is desirable, such a material appears to reduce thestructural integrity of the nestable element.

Furthermore, fiber embedded polymers increase the rigidity of nestableelements 30 so that longitudinal contraction of overtube 22 issignificantly reduced when the overtube is stiffened. Longitudinalcontraction develops when tension wires 36 are actuated to apply acompressive clamping load to overtube 22. The resultant pressureeliminates any gaps between adjacent elements 30 and deflects theproximal portion of each nestable element radially outward. Thisforeshortens each element in the longitudinal direction, so thatovertube 22 contracts in the axial length.

Typically, an overtube made from polymeric nestable elements withoutinclusion of glass and/or carbon fibers will contract approximately8-12% in the longitudinal direction when a compressive force ofapproximately 30 lbs is applied. By comparison, when a compressive loadof 30 lbs is applied to nestable elements made from a glass and/orcarbon fiber embedded polymer, as in the preferred embodiment of thepresent invention, the overtube only contracts approximately 4%.Advantageously, this reduces trauma to the patient by providing greateraccuracy during use of the present invention, which is particularlyimportant in delicate procedures. In addition to glass and/or carbonfilled polymers, it will be apparent to one of ordinary skill in the artthat nestable elements 30 also may be molded or machined from otherpolymers and/or metals, such as polyurethane, polyvinyl chloride,polycarbonate, nylon, titanium, tungsten, stainless steel, aluminum, orcombinations thereof. Indeed, nestable elements 30 made from metalsexperience a longitudinal contraction even less than that experienced byfiber embedded polymers. These materials are provided only for the sakeof illustration, and one of ordinary skill in the art will recognizenumerous additional materials that are suitable for use with theapparatus of the present invention.

Referring now to FIG. 4, an illustrative embodiment of distal region 23and atraumatic tip 24 is described. Distal region 23 comprises flexible,kink-resistant coil 41 encapsulated in flexible layer 42. Layer 42preferably comprises a soft elastomeric and hydrophilic coated material,such as silicon or synthetic rubber, and terminates at the distal end inenlarged section 44 that forms atraumatic tip 24. At the proximal end,layer 42 joins with or is integrally formed with liner 43 that extendsthrough bores 33 of nestable elements 30 to handle 21. In a preferredembodiment, liner 43 is made of a thin, flexible material optionallyhaving flexible, kink-resistant coil 29 embedded therein. The materialof liner 43 preferably has a high durometer within the range of 30-80 D,but also may have a lower or higher durometer.

Layer 42 preferably joins with or is integrally formed with flexibleelastomeric skin 45 to form sheath 48, which encapsulates nestableelements 30 in annular chamber 46. Skin 45 provides a relatively smoothouter surface for overtube 22, and prevents tissue from being capturedor pinched during relative rotation of adjacent nestable elements 30. Ina preferred embodiment, aggregate thickness T of skin 45, nestableelements 30 and liner 43, is less than or equal to approximately 2.5 mm,and more preferably less than or equal to 1 mm. For example, skin 45 mayhave a thickness of 0.13 mm, or more preferably 0.1 mm, element 30 mayhave a thickness of 1.9 mm, and more preferably 0.7 mm, and liner 43 mayhave a thickness of 0.38 in, or more preferably 0.15 mm.

In accordance with one aspect of the present invention, colonoscope 10may be positioned with its distal tip 11 disposed in distal region 23,so that deflection of steerable distal tip 11 imparts an angulardeflection to distal region 23 and atraumatic tip 24. To ensure thatthere is no gross relative motion between colonoscope 10 and apparatus20, Toughy-Borst valve 26 is tightened to engage apparatus 20 to thecolonoscope. In this manner, colonoscope 10 and distal region 23 may besimultaneously advanced through the colon, with the distal tip of thecolonoscope providing a steering capability to apparatus 20. Apparatus20 therefore may be advantageously advanced together with colonoscope 10when overtube 22 is in the flexible state, reducing relative motionbetween apparatus 20 and colonoscope 10 to those instances whereovertube 22 must be shape-locked to prevent distension of the colon.

Still referring to FIG. 4, terminations 47 of tension wires aredescribed. Terminations 47 illustratively comprise balls welded ormolded onto the ends of tension wires 36 that ensure the tension wirescannot be pulled through tension wire bores 35 of the distal-mostnestable element 30. This ensures that the nestable elements cannot comeloose when overtube 22 is disposed within a patient.

Alternatively, terminations 47 may comprise knots formed in the ends oftension wires 36, or any suitable fastener that prevents the tensionwires from being drawn through the tension wire bores of the distal-mostnestable element. Advantageously, skin 45 provides additional assurancethat all of nestable elements 30 can be safely retrieved from apatient's colon in the unlikely event of a tension wire failure.

Referring now to FIGS. 2 and 5, tension wires 36 within overtube 22,liner 43 and lumen 25 extend from distal region 23, through overtube 22,and to handle 21. Within handle 21, each tension wire 36 passes throughwire lock release 51 fixedly attached to handle 21, and wire lock 52disposed on slide block 53. Each tension wire 36 terminates at wiretension spring 54, which maintains tension wires 36 in light tensioneven when overtube 22 is in the flexible state. The degree of tensionprovided by wire tension springs 54 is not sufficient to clamp adjacentnestable elements 30 together, but on the other hand does not let gapsform between adjacent nestable elements, and helps to manage the tensionwire take up or slack as overtube 22 makes various bends.

Slide block 53 is keyed to slide along rail 55 disposed between limitblocks 56 and 57, and comprises a rigid block having a bore throughwhich rail 55 extends and an additional number of bores as required forthe number of tension wires 36 employed. Rack gear 58 is fixedly coupledto slide block 53. Rack 58 mates with pinion gear 59, which is in turndriven by bi-directional pawl 60 coupled to actuator 27. Pinion gear 59may be selectively engaged by either prong 61 or 62 of bi-directionalpawl 60, depending upon the position of selector switch 63.

If prong 61 is selected to be engaged with pinion gear 59, a squeezingaction applied to actuator 27, illustratively hand grip 64, causes rack53 to move in the D direction in FIG. 5, thereby applying tension totension wires 36. Repeated actuation of hand grip 64 causes slide block53 to move progressively further in direction D, thereby applying anincreasing clamping load on nestable elements 30. Any slack lengths oftension wires 36 extending below slide block 53 are taken up by wiretension springs 54. As discussed in greater detail below with respect toFIG. 6, wire locks 52, which are affixed to slide block 53, engage andretract tension wires 36 concurrently with movement of slide block 53 inthe D direction.

If prong 62 is instead chosen by selector switch 63 to engage piniongear 59, repeated actuation of hand grip 64 causes slide block 53 totranslate in direction U, thereby relaxing the tensile load applied bytension wires 36 to nestable elements 30. Repeated actuation of handgrip 64 causes slide block 53 to advance in direction U until wire lockreleases 51 engage wire locks 52, releasing all tension from tensionwires 36 except that provided by wire tension springs 54. This actionpermits the clamping forces imposed on nestable elements 30 to beprogressively reduced and render overtube 22 progressively moveflexible, until when wire lock releases 51 engage wire locks 52, theovertube is returned to its most flexible state.

Referring to FIG. 6, wire lock 52 and lock release 51 are described ingreater detail. Wire lock 52 includes jaws 65 disposed within collet 66.Collet 66 includes a tapered conical bore 67. Jaws 65 have rampedexterior surfaces 68 and teeth 69, and are biased against the surfaceformed by the tapered conical bore by springs 70. Teeth 69 areconfigured to engage tension wire 36 under the bias force of springs 70.When slide block 53 is moved in direction D (see FIG. 5), jaws 65 engageand grasp tension wire 36 and retract the tension wire in direction D.

To disengage teeth 69 from tension wire 36, e.g., when it is desired toallow overtube 22 to return to a flexible state, slide block 53 isactuated as described previously to move in direction U. Furtheractuation of slide block 53 towards limit block 56 and wire lock release51 causes wire lock release 51 to extend into tapered conical bore 67and push jaws 65 backward against the bias of springs 70. Once tensionwires 36 are freed from jaws 65, overtube 22 returns to its mostflexible state.

Referring to FIGS. 7A-7C, a method of using apparatus 20 is described.Colonoscope 10 and overtube 22 may be inserted into the patient eithersimultaneously or by first backloading the overtube onto thecolonoscope. To perform simultaneous insertion, colonoscope 10 isintroduced into lumen 25 of handle 21 until distal tip 11 of thecolonoscope is disposed in distal region 23. Toughy-Borst valve 26 isactuated to lock apparatus 20 to colonoscope 10. As one unit,colonoscope 10 and overtube 22 are inserted into rectum R of thepatient, and navigated about rectosigmoid junction RJ. As discussedpreviously, steerable distal tip 11 may be used to impart angulardeflection to flexible tip 24 to steer tip 24 about tortuous curves,such as rectosigmoid junction RJ. Once distal tip 11 and tip 24 havebeen negotiated past rectosigmoid junction RJ, the current shape ofovertube 22 is locked in the manner discussed above to provide a rigidchannel through which colonoscope 10 may be further advanced into thecolon without distending rectosigmoid junction RJ. Once distal tip 11 ofcolonoscope 10 is negotiated past sigmoid colon SC, overtube 22 isreleased from its rigid state and advanced along colonoscope 10 until ittoo traverses sigmoid colon SC. Again, the current shape of overtube 22is locked to provide a rigid channel for advancement of colonoscope 10.To negotiate the remainder of the colon, such as left colic flexure LCFand right colic flexure RCF, the preceding steps may be repeated. Inthis manner, colonoscope 10 and overtube 22 may be navigated through thetortuous curves of the colon without distending the colon, and therebycausing discomfort, spasm or injury.

Alternatively, rather than simultaneously inserting both colonoscope 10and overtube 22 into the patient, apparatus 20 first may be backloadedonto the colonoscope. First, overtube 22 is threaded onto colonoscope 10and positioned proximal distal tip 11, as shown in FIG. 8. Colonoscope10 then is inserted into rectum R of the patient and advanced aroundrectosigmoid junction RJ. Overtube 22 is advanced along colonoscope 10into rectum R of the patient, using colonoscope 10 as a guide rail tonegotiate rectosigmoid junction RJ. Once overtube 22 traversesrectosigmoid junction RJ to the position shown in FIG. 7A, the shape ofovertube 22 is locked to provide a rigid channel through whichcolonoscope 10 may be further advanced into the colon. To negotiate theremainder of the colon, the steps discussed in reference to FIGS. 7B-7Cmay be performed.

With respect to FIG. 9, an alternative embodiment of handle 21 isdescribed. Like handle 21 of FIG. 5, handle 71 also embodies aratchet-type tension mechanism, but in this embodiment overtube 22 maybe separated from handle 71, thereby permitting handle 71 to besterilized for repeated use. Handle 71 comprises housing 72 havingactuator 73 that engages teeth 74 disposed along the length of rod 75,which defines working axis W of handle 71. Push knob 76 is affixed tothe proximal end of rod 75 so that when pawl 77 is released, rod 75 maybe pushed in a distal direction. Pawl 77 engages teeth 74 of rod 75 toprevent distally-directed motion of rod 75. Spring 78 biases pawl 77against teeth 74 of rod 75, to provide a one-way ratchet effect whenactuator 73 is squeezed.

As in the embodiment of FIG. 5, tension wires 36 extend through wirelock releases 79, wire locks 80, and are coupled to wire tension springs81. Wire locks 80 are affixed to block 82, which translates withinhousing 72 responsive to movement of rod 75. Wire locks 80 and wire lockreleases 79 operate in the same manner as described with reference toFIG. 6.

In operation, squeezing actuator 73, illustratively a hand grip, causesfork 83 to move rod 75 in a proximal direction so that pawl 77 capturesthe next distal-most tooth 74. This movement also causes wire locks 80to engage and grasp tension wires 36 and retract the tension wiresproximally. Further actuation of actuator 73 causes overtube 22 tostiffen in the manner previously described. Spring 78 retains pawl 77 incontinuous engagement with teeth 74, thereby preventing rod 75 frommoving in the distal direction.

When it is desired to make overtube 22 more flexible, pawl 77 isreleased and knob 76 pushed in the distal direction so that wire locks80 engage wire lock releases 79. As described above, this releasestension wires 36 from wire locks 80 and permits overtube to assume itsmost flexible state.

In accordance with one aspect of the present invention, overtube 22 ofthe embodiment of FIG. 9 may be replaceably removed from yoke 84 ofhandle 71. In addition tension wires 36 further may comprise connectors85 that permit the tension wires to be disconnected. Such aconfiguration permits the overtube to be removed and discarded after asingle use, while the handle may be sterilized and reused.

Yoke 84 is also configured to position overtube 22 so that longitudinalaxis L of the overtube is angularly displaced from working axis W by apredetermined angle β. This arrangement prevents handle 71 frominterfering with advancement of colonoscope 10 into lumen 25.

In accordance with yet another aspect of the present invention, overtube22 includes atraumatic tip 86 that comprises a soft foam-like material.Atraumatic tip 86 not only facilitates advancement of overtube 22 intraversing tortuous anatomy, but also serves to retain the organ wall asafe distance away from the opening through which the colonoscope isreciprocated by radially expanding the organ wall in the vicinity of thetip, as described hereinbelow with respect to FIG. 14A. Accordingly,atraumatic tip 86 reduces the potential for tissue to be caught orpinched in lumen 25 when the colonoscope is manipulated.

Referring now to FIGS. 10-16, alternative tensioning mechanisms aredescribed, in which the tensioning mechanisms may provide a fail-safemode that reduces the risk of undesired reconfiguration of the overtubein the event of tensioning mechanism failure. When overtube 22 is in therigid state, the following tensioning mechanisms are configured toself-equalize compressive loads applied to the multiplicity of nestableelements, so that if, e.g., a tension wire breaks, the overtube eithersoftens into the flexible state or retains its shape-locked state.

FIG. 10A schematically depicts components of a first embodiment of analternative tensioning mechanism having plurality of distal pulleys 87operably coupled via proximal tension wire 88. Proximal tension wire 88is slidably disposed within proximal pulley 89. Each tension wire 90couples adjacent tension wire lumens 28, through respective distalpulleys 87. For example, if four tension wire lumens 28 a-28 d areprovided, as in FIG. 10A, first tension wire 90 a extends from tensionwire lumen 28 a to adjacent tension wire lumen 28 b through first distalpulley 87 a. Likewise, second tension wire 90 b extends from tensionwire lumen 28 c to adjacent tension wire lumen 28 d through seconddistal pulley 87 b.

This configuration equalizes tension within tension wires 90, so that aproximally directed force F applied to proximal pulley 89 is distributedevenly through tension wires 90. When one of the tension wires breaks,this configuration allows overtube 22 to soften into its flexible statesince the loss of tension in any of the tension wires is transmittedthrough the pulley system to the remaining tension wires.

It will be apparent to one of ordinary skill in the art that tensionwires 90 a and 90 b may comprise either two separate lengths of wire, ora single length of wire that is looped backwards after traversing thedistal-most nestable element 30. Furthermore, while FIG. 10A depictstension wires 90 extending through adjacent tension wire lumens 28, thetension wires instead may extend through wire lumens disposeddiametrically opposite each other, as shown in FIG. 10B. Tension wires90 preferably are made from a superelastic material, e.g., nickeltitanium alloy, but also may be made from braided stainless steel,single stainless steel wires, Kevlar, a high tensile strengthmonofilament thread, or combinations thereof. These materials areprovided only for the sake of illustration and should in no way beconstrued as limiting.

In an alternative embodiment illustrated in FIG. 10C, proximal pulley 89is eliminated, and distal pulleys 87 are fixed to each other, e.g., bywelding, so that a unitary pulley manifold is formed. A proximallydirected force F that is applied to the pulley manifold is distributedevenly through tension wires 90 that extend through respective distalpulleys 87 to diametrically disposed tension wire lumens 28 withinovertube 22. If tension wires 90 comprise two separate lengths of wires,the risk of reconfiguration of overtube 22 is reduced if one of thewires breaks since the tension within the overtube, as defined by theunbroken tension wire, is symmetrically balanced. If the remainingtension wire breaks, the tension wire relaxes into the flexible state.If tension wires 90 comprise a single length of wire that breaks, theovertube immediately relaxes into the flexible state, thereby alsoreducing the risk of undesired configuration of the overtube in theevent of tensioning system failure.

Furthermore, applicants have observed that the apparatus of the presentinvention also may comprise only one distal pulley 87 coupled toovertube 22 via a single tension wire 90 disposed through diametricallyopposite tension wire lumens 28. When a proximally directed force isapplied to the single distal pulley, the force is distributed throughthe single tension wire to impose a symmetrical compressive clampingload on overtube 22 that is sufficient to shape-lock the overtube. Whentension wire 90 breaks, overtube 22 immediately softens into itsflexible state, thereby reducing the risk of undesired reconfigurationof the overtube in the event of tensioning system failure.

Referring now to FIG. 11, lumen 25 and tension wires 90 within overtube22 extend from the distal region of the apparatus, through overtube 22,and to handle 91. Within handle 91, the tension wires are slidablycoupled to distal pulleys 87, which in turn are slidably coupled toproximal pulley 89. Proximal pulley 89 is coupled to and translates withslide block 92, that is keyed to travel along track 93 disposed withinhousing 94. Plunger 95 is mounted pivotally to slide block 92 at theproximal end and slidably disposed within plunger housing at a distalend.

Plunger housing 96 is mounted pivotally to actuator 27, illustrativelyhand grip 97. To bias hand grip 97 against actuation absent anexternally applied force, compression spring 98 is providedconcentrically disposed about plunger 95. Compression spring 98maintains tension wires 90 in constant tension when the tensioningmechanism is actuated to impose a clamping load. Advantageously, ifadjacent nestable elements shift slightly when overtube 22 isshape-locked, the proximal bias of compression spring 98 immediatelyadvances slide block 92 in the proximal direction to maintain arelatively constant tension load within tension wires 90, therebyreducing the risk of reconfiguration of the overtube back to theflexible state that otherwise may occur absent compression spring 98.

Hand grip 27 also includes pawl 99, which is disposed to engage teeth100 on ratchet bar 101 to prevent distally-directed motion of slideblock 92. Ratchet bar 101 is pivotally mounted in housing 94 with aspring (not shown) that, with the aid of compression spring 98, biasespawl 99 against teeth 100 of ratchet bar 101, to provide a one-wayratchet effect when hand grip 97 is squeezed.

In operation, squeezing hand grip 97 causes pawl 99 to capture the nextproximal-most tooth 100. This movement also provides a compressive forceto compression spring 98 that is transmitted to slide block 92. Theproximally-directed component of the compressive force causes slideblock 92 to translate along track 93, proximally retracting tensionwires 90 so that a clamping load is imposed on the nestable elementswithin overtube 22. Further actuation of hand grip 97 causes overtube 22to stiffen progressively in the manner previously described.

Advantageously, proximal-most tooth 100 a is disposed on ratchet bar 101at a predetermined proximal location that permits a single actuation ofhand grip 97 to completely transition overtube 22 from its flexiblestate to its shape-fixed state. Furthermore, as pawl 99 advances handgrip 97 closer to housing 94, the mechanical advantage of the actuationof the hand grip increases. More specifically, as hand grip 97 becomesincreasingly horizontal, the proximally-directed component of the forcetransmitted by compression spring 98 increases in magnitude.Accordingly, more force is transmitted to increase tension withintension wires 90, and thus increase the clamping load applied torigidize overtube 22.

When it is desired to transition overtube 22 into the flexible state,pawl 99 is released from engagement with teeth 100 by rotating ratchetbar 101 in the proximal direction. The release of the compressive loadapplied to compression spring 98 causes hand grip 97 to rotate in thedistal direction and slide block 92 to retract in the distal direction.This sufficiently relaxes tension wires 90 so that the tension wiresretain little to no tension, thereby permitting overtube 22 to assumeits most flexible state.

Referring now to FIGS. 12A-12D, alternative embodiments of fail-safetensioning mechanisms are described, in which the plurality of pulleysof the previous embodiment is replaced by a single pulley manifold. InFIG. 12A, a first embodiment of a pulley manifold is described. Pulleymanifold 110 includes body 111 having central bore 112 that accommodatescolonoscope 10, first and second grooves 113 a and 113 b that eachaccept a tension wire, and are milled or molded into lateral surface 114of body 111, and yoke 115 that is configured to couple pulley manifold110 to an actuator (not shown).

First groove 113 includes a curved track that terminates at first distalends 116 a disposed diametrically opposite each other at distal surface117. Second groove 113 b also comprises a curved track that crossesfirst groove 113 a at intersection 118, and terminates at second distalends 116 b. Second distal ends 116 b are disposed at distal surface 117diametrically opposite each other and preferably 45° from first distalends 116 a. Similar to distal pulleys 87 of FIG. 10B, each grooveaccepts a tension wire that extends through diametrically disposedtension wire lumens within overtube 22. To reduce friction betweentension wires 90 a and 90 b at intersection 118, first groove 113 a mayhave a greater depth than that of second groove 113 b, or vice versa. Toprevent tension wires 90 from disengaging from grooves 113, a sleeve(not shown) may be disposed around pulley manifold 110.

If tension wires 90 comprise two separate lengths of wires, the risk ofreconfiguration of overtube 22 is reduced if one of the wires breakssince the tension within the overtube, as defined by the unbrokentension wire, is symmetrically balanced. If the remaining tension wirebreaks, the overtube relaxes into the flexible state. If tension wires90 comprise a single length of wire, the overtube immediately relaxesinto the flexible state if the single wire breaks. Accordingly, pulleymanifold 110 provides overtube 22 with a fail-safe mode that reduces therisk of reconfiguration of the overtube in the event of tensioningmechanism failure.

FIG. 12B depicts pulley manifold 110, in which the yoke is replaced withthird groove 120. Third groove 120 is milled or molded into lateralsurface 114, and accepts an additional tension wire 121 that may becoupled to actuator 27 (see FIG. 2). When a proximally directed force Fis applied to tension wire 121, the force imposes tension to tensionwires 90. Third groove 120 includes a curved track that terminates atthird distal ends 122, which preferably are diametrically disposedopposite each other at proximal surface 123 of pulley manifold 110.

With respect to FIGS. 12A and 12B, an alternative embodiment of a pulleymanifold is described. Rather than having grooves disposed on a lateralsurface of the pulley manifold, pulley manifold 130 incorporates firstand second grooves 131 a and 131 b that terminate at tension wire bores132 disposed through body 133. Preferably, tension wire bores 132 areequidistantly and circumferentially disposed on proximal surface 136.Pulley manifold 130 also incorporates central bore 134 that accommodatescolonoscope 10, and yoke 135 that couples pulley manifold 130 toactuator 27 (see FIG. 2).

In FIG. 12C, first and second grooves 131 a and 131 b are milled ormolded in overlapping fashion. To reduce friction between tension wiresdisposed within the overlapping portion of the grooves, first groove 131a may have a depth greater than that of second groove 131 b, or viceversa. In FIG. 12D, the first and second grooves do not overlap, firstgroove 131 a having a smaller radius of curvature than that of secondgroove 131 b.

Applicants also contemplate that either the first or second groove ofthe pulley manifolds of FIGS. 12A-12D may be eliminated so that aproximal force F applied thereto would impose a symmetrical compressiveclamping force to overtube 22 through a single length of tension wire 90that extends through diametrically disposed tension wire lumens.Accordingly, when tension wire 90 or 121 breaks, or yoke 115 fails, theovertube relaxes back into its flexible state, thereby reducing the riskof undesired reconfiguration of the overtube.

Referring now to FIGS. 13A and 13B, handle 140 is described employingpulley manifold 110 of FIG. 12B. Tension wires 90 within overtube 22,skin 45, liner (not shown for illustrative purposes) and lumen 25 extendfrom distal region 23 (see FIG. 2), through overtube 22, and to handle140, which preferably measures less than or equal to 5 inches, similarto the other handle embodiments described herein. Within handle 140,tension wires are slidably coupled to pulley manifold 110, which rideswithin cylindrical extension 141 and cylinder 142. Cylindrical extension141 may be integrally manufactured with housing 143, and is configuredto be inserted into a patient's rectum. Concentric with cylindricalextension 141, cylinder 142 defines the proximal portion of lumen 25disposed within handle 140.

Via additional tension wire 121, pulley manifold 110 is coupled to slideblock 92, which is keyed to translate in track 93. As in handle 91 ofFIG. 11, plunger 95 is coupled pivotally to slide block 92 at a proximalend, and slidably disposed within plunger housing 96 at a distal end.Concentrically disposed about plunger 95, compression spring 98 biaseshand grip 97 from being actuated absent an externally applied force. Asin FIG. 11, compression spring 98 maintains the level of tension withintension wires 90 if adjacent nestable elements shift slightly whenovertube 22 is in the rigid state, thereby reducing the risk ofreconfiguration of the overtube back to the flexible state.

Hand grip 97 also includes pawl 99, which is configured to engage tooth144 of ratchet bar 145 to prevent distally-directed motion ofslide-block 92. Tooth 144 is disposed on ratchet bar 145 at apredetermined proximal location that permits a single actuation of handgrip 97 to completely transition overtube 22 from its flexible state toits shape-fixed state. Ratchet bar 145 is mounted pivotally in housing143 with a spring (not shown) that, with the aid of compression spring98, biases pawl 99 against tooth 144. To release tension from tensionwires 90, pawl 99 may be released from engagement with tooth 144 byrotating ratchet bar 145 in the proximal direction. This sufficientlyrelaxes tension wires 90 so that the tension wires retain little to notension, thereby permitting overtube 22 to assume its most flexiblestate.

Handle 140 also has shield 146 coupled to a distal end thereof. Shield146 prevents handle 140 proximal thereto from inadvertently beinginserted into the patient's rectum. Handle 140 also incorporatesindicator 147 (FIG. 13B) that provides a clinician with informationabout the rigidity of overtube 22. Indicator 147 comprises slot 148disposed through a wall of housing 143, pointer 149 disposed throughslot 148, and scale 150 disposed on an external surface of housing 143adjacent to slot 148. Pointer 149 is coupled to translation of proximalmanifold 110 so that it translates with the manifold. Scale 150incorporates color gradations, or indicia (not shown) to indicate therigidity of overtube 22. Of course, it will be obvious to one ofordinary skill in the art that pointer 149 may be coupled to anystructure within handle 140 that moves when actuator 27 is actuated,e.g., slide block 92 or pawl 99. Alternatively, handle 140 may include aforce sensor coupled between the distal end of track 93 and slide block92.

It also will be evident to one of ordinary skill in the art that any ofthe handle embodiments described herein also may incorporate cylindricalextension 141 for insertion into a patient's rectum, one tooth 144 on aratchet bar to transition the overtube from a flexible state to a rigidstate with a single actuation of actuator 27, shield 146 to preventinsertion of the handle into the patient's rectum, indicator 147 toprovide a clinician with information about the rigidity of the overtube,and combinations thereof.

Referring now to FIGS. 14A-14C, yet another alternative embodiment of atensioning mechanism suitable for use with the apparatus of the presentinvention is described. Handle 160 is adapted to reconfigure theovertube between its flexible and rigid states with successiveactuations of actuator 27. Handle 160 has housing 161 containingplurality of fixed pillars 162 that are circumferentially andazimuthally disposed around inner cylindrical chamber 163 of housing161. Each fixed pillar 162 has beveled concavity 164 disposed on aproximal end adjacent beveled arm 165. Channel 166 is disposed betweenadjacent pillars 162.

Handle 160 also incorporates compression spring 167 proximally disposedto bias rotatably mounted manifold 168 against plurality of pillars 162.Manifold 168 incorporates plurality of distally projecting posts 169having beveled distal ends 170 with inclination angles that match thoseof beveled concavities 164 and beveled arms 165. Accordingly, whenbeveled distal ends 170 are forcefully engaged with beveled concavities164, a component of the force imparted by posts 169 causes manifold 168to rotate, absent the presence of beveled arm 165. Likewise, when thebeveled distal ends are engaged with beveled arms 165, a component ofthe force imparted by posts 169 rotates the manifold so that pillars 162are disposed at the proximal ends of channels 166.

Also attached to manifold 168 is tension spring 171, that in turnpreferably is coupled to one of the pulley systems of FIGS. 10A-10C or12A-12D. Tension spring 171 maintains tension wires 90 in constanttension if nestable elements disposed within the overtube slightly shiftwhen the overtube is rigidized. Accordingly, this reduces the risk ofreconfiguration of the overtube into the flexible state that otherwisewould occur absent tension spring 171.

Handle 160 further comprises translatable cylindrical collar 172 havingproximally projecting teeth 173. Each tooth has an inclination anglethat substantially is equivalent to that of beveled distal ends 170 ofmanifold 168. Accordingly, when teeth 173 are engaged forcefully withbeveled distal ends 170, a component of the force imparted by the teethrotates the manifold. Also coupled to collar 172 is actuator 27,illustratively translatable hand grip 174, that may be squeezed againststationary hand grip 175 to retract collar 172 in the proximal directionto contact beveled distal ends 170 of manifold 168.

FIG. 14B depicts the configuration of handle 160 when an overtubecoupled thereto is in the rigidized state. Beveled distal ends 170 ofmanifold 168 are engaged within concavities 164 of pillars 162. When itis desired to reconfigure the overtube into its flexible state,translatable hand grip 174 is squeezed against stationary hand grip 175.This action translates collar 172 in the proximal direction. When teeth173 engage beveled distal ends 170, continual proximal advancement oftranslatable hand grip 174 causes collar to push manifold 168 in theproximal direction against compression spring 167. When beveled distalends 170 clear beveled arm 165, the forces imparted by teeth 173 to thebeveled distal ends rotate manifold 168 so that beveled distal ends 170are engaged to beveled arms 165, as shown in FIG. 14B.

Retraction of collar 172 disengages teeth 173 from manifold 168. Theforces imparted by beveled arm 165 to the beveled distal ends rotatemanifold 168 until the beveled distal ends clear pillar 162. Thereafter,the bias of compression spring 167 advances plurality of posts 169 intochannels 166. FIG. 14C depicts this configuration, in which the overtubeis in its flexible state.

To reconfigure the overtube back into its rigid state, translatable handgrip 174 again is squeezed against stationary hand grip 175. Thisproximally advances collar 172 until teeth 173 contact beveled distalends 170 of posts 169. Continual proximal actuation of translatable handgrip 174 causes collar 172 to push posts 169 out of channels 166. Whenbeveled distal ends 170 clear pillars 162, the forces imparted by teeth173 to beveled distal ends 170 rotate manifold 168. Distal retraction ofcollar 172 disengages teeth 173 from manifold 168, and the bias ofcompression spring 167 advances manifold 168 until beveled distal ends170 completely engage concavities 164.

Referring now to FIG. 15, still another alternative embodiment of handle21 suitable for use with the apparatus of the present invention isdescribed. Handle 180 comprises housing 181 containing lumen 25 of theovertube. Handle 180 further includes piston 182 translatably disposedwithin piston housing 183, which is coupled in pneumatic communicationvia port 184 and tube 185 with a pressure source (not shown). Attachedto piston shaft 186 is pulley 187 around which proximal tension wire 188is disposed. Proximal tension wire 188 is affixed to housing 181 at itsproximal end 189 and to tension spring 190 at its distal end.Preferably, tension spring 190 distally is coupled to one of the pulleysystems of FIGS. 10A-10C or 12A-12D. Similar to tension spring 171 ofFIGS. 14A-14C and compression springs 98 of FIGS. 11 and 13, tensionspring 190 maintains the tension wires in constant tension when theovertube is in the shape-locked state. This reduces the risk ofreconfiguration of the overtube to its flexible state if nestableelements disposed therein slightly shift relative to adjacent nestableelements.

To stiffen the overtube, the pressure source may be actuated to infusepiston housing 183 with pressurized air that proximally advances piston182. This in turn advances pulley 187 in the proximal direction, so thattension is applied to proximal tension wire 188. That tension istransmitted through tension spring 190 to tension wires disposed withinthe overtube, thereby imposing a compressive clamping load to adjacentnestable elements disposed within the overtube. To transition theshape-locked overtube into the flexible state, the pressure source maybe actuated to remove air from piston housing 183. This retracts piston182 and pulley 183 in the distal direction, thereby releasing thecompressive clamping load applied to the overtube.

Pursuant to another aspect of the present invention, tension spring 190may be replaced with a damper per se known in the art. In addition tothe advantages provided by the tension spring, the damper allows tensionwithin proximal tension wire 188, and thus tension wires disposed withinthe overtube, to be slowly released. Applicants contemplate that adamper may replace any of the compression and tension springs describedherein.

Referring now to FIG. 16, apparatus 20 may be provided with a tensioningmechanism that is selectively operable to transition overtube 22 betweenthe flexible and rigid states substantially without proximal movement ofdistal region 23 (see FIG. 2). In FIG. 16, tension wire 196 and lumen 25extend from distal region 23, through overtube 22, and to handle 195.Within handle 195, tension wire 196 is slidably coupled to pulleymanifold 197 that is rigidly or rotatably affixed to distal end 198 ofthe handle. Pulley manifold 197 preferably includes orthogonallydisposed first and second channels 199 a and 199 b. While FIG. 16depicts only one tension wire, it should be understood that a secondtension wire preferably is disposed through second channel 199 b andnestable elements 30.

Similar to the tensioning mechanisms of FIGS. 12A-12D and 13, thepresent tensioning mechanism also provides overtube 22 with a fail-safemode. If the tension wires disposed through channels 199 comprise twoindependent wires, the load within overtube 22 remains symmetricallydistributed when one of the wires breaks. Thus, the risk ofreconfiguration of overtube 22 is reduced. If these tension wirescomprise a single length of wire, overtube 22 will relax into theflexible state if the single length of wire breaks.

Between pulley 197 and nestable elements 30, tension wire 196 alsoextends through collar 200, which has distal surface 201 that iscontoured to mate with proximal surface 32 of the proximal-most nestableelement 30. Collar 200 is disposed to translate within housing 202 sothat distal surface 201 engages proximal surface 32 of nestable element30 when collar 220 is advanced in the distal direction.

Collar 200 pivotally is connected to plunger 95, which is slidablydisposed within plunger housing 96. Plunger housing 96 in turn ismounted pivotally to actuator 27, illustratively hand grip 97. To biashand grip 97 against actuation absent an externally applied force, andto maintain constant tension within tension wire 196 when overtube 22 isrigidized, compression spring 98 is provided concentrically disposedabout plunger 95.

Hand grip 97 also includes pawl 99, which is disposed to engage teeth100 on ratchet bar 101 to prevent proximally-directed motion of collar200. Ratchet bar 101 pivotally is mounted in housing 202 with a spring(not shown) that, with the aid of compression spring 98, biases pawl 99against teeth 100 of ratchet bar 101. Handle 195 also may incorporateannular extension 203 that is disposed surrounding collar 200 and thatmay be inserted into a patient's rectum.

Similar in operation to handle 91 of FIG. 11, when hand grip 97 issqueezed, pawl 99 engages the next distal-most tooth 100. This actionalso transmits force through compression spring 98, which pushes collar200 into engagement with the proximal-most nestable element. Continualactuation of hand grip 97 causes collar 200 to exert an increasingcompressive clamping load to nestable elements 30, which causes overtube22 to stiffen into its shape-locked state.

Advantageously, this configuration permits overtube 22 to reconfigurebetween the flexible and rigid states without substantial proximalmovement of the distal end of the overtube. In previous embodiments,nestable elements 30 are advanced in the proximal direction whenovertube 22 is rigidized, and due to compression of adjacent nestableelements, overtube 22 shortens in length. In contrast, when the presentembodiment advances the nestable elements in the distal direction,overtube 22 maintains its length despite compression of adjacentnestable elements since the length of the overtube substantially islimited by the length of tension wire 196. This provides greateraccuracy when using the apparatus of the present invention, and isparticularly useful in delicate procedures.

It will be apparent to one of ordinary skill in the art that, similar tothe tensioning mechanism described in reference to FIG. 13, ratchet bar101 may be provided with only one tooth. Alternatively, with minormodifications that will be evident to one of ordinary skill in the art,the tensioning system of FIGS. 14A-14C may be coupled to collar 200 totransition overtube 22 between the flexible and rigid states withsuccessive actuations of actuator 27, or the piston mechanism describedin reference to FIG. 15 may be coupled to collar 200 to drivetranslation thereof. More specifically, rather than being pivotallycoupled to plunger 95, collar 200 instead may be fixedly coupled to apiston disposed to provide motion along the longitudinal axis of collar200. Furthermore, second channel 199 b may be eliminated from pulleymanifold 197 so that a single tension wire may translatably extendthrough first channel 199 a and diametrically disposed tension wirebores disposed within collar 200 and nestable elements 30. When thesingle tension wire breaks, the overtube relaxes into the flexible stateimmediately, thereby providing a fail-safe mode that reduces the risk ofundesired reconfiguration of the overtube.

With respect to FIGS. 17A and 17B, an alternative structure is describedto facilitate movement of a colonoscope within lumen 25 of overtube 22.In particular, instead of using inner lining 43 as depicted in FIG. 4,some or all of nestable elements 30 may include roller bearings 205 thatare received in insets 206 formed in nestable elements 30. Bearings 205may be disposed on ring 207 to facilitate assembly of the device.

FIGS. 18A and 18B depict a further alternative embodiment, in whichlubricious flexible rails 208 are disposed within bore 33 of nestableelements 30. Rails 208 span the length of lumen 25, and reduce contactbetween the colonoscope and the interior of the overtube, therebyfacilitating movement of the colonoscope through overtube 22.

In FIGS. 19 and 20, still further alternative structures are describedto facilitate movement of a colonoscope within lumen 25 of overtube 22.More specifically, rather than using liner 43 as shown in FIG. 4, someor all of nestable elements 30 may incorporate hydrophilically-coatedpolymeric layer 209, which may be disposed surrounding distal portion210 of bore 33.

Alternatively, as described in FIGS. 20A and 20B, overtube 22 maycomprise multiplicity of frustoconical elements 215 that, when nested,provide a smooth inner lumen to accommodate colonoscope 10 without theneed for a separate liner. Each frustoconical element 215 includescentral bore 216, and at least two or more tension wire bores 217.Central bore 216 is defined by cylindrical distal inner surface 218 thathas a substantially constant diameter, and proximal inner surface 219that is continuous with distal inner surface 218.

Proximal inner surface 219 is slightly curved in a radially outwarddirection so that, when tension wires 36 are relaxed, proximal innersurface 219 can rotate relative to external surface 220 of an adjacentelement. External surface 220 of each frustoconical element may bestraight or contoured to conform to the shape of proximal inner surface219, and tapers each element so that distal end 221 is smaller in outerdiameter than proximal end 222. When frustoconical elements 215 arenested together, distal inner surface 218 of each frustoconical elementis disposed adjacent to the distal inner surface of an adjoiningfrustoconical element.

Advantageously, the present configuration provides lumen 25 with asubstantially continuous profile. This permits smooth advancement ofcolonoscope 10 therethrough, and thereby eliminates the need to disposea separate liner within lumen 25. To provide a lubricious passageway tofurther facilitate advancement of the colonoscope, each frustoconicalelement optionally may incorporate an integral hydrophilic polymericlining as described with respect to the preceding embodiment of FIG. 19,or a thin, flexible lining having a hydrophilic coating may be disposedthrough lumen 25.

In FIGS. 21A-21C, yet another alternative structure is described, inwhich distal surface 31 of each nestable element is macroscopicallytextured to increase the friction between adjacent nestable elements 30when a compressive clamping load is applied to overtube 22.Illustratively, each element 30 may incorporate multiplicity of divots225 disposed on distal surface 31, and teeth 226 that are disposed onproximal surface 32 adjacent proximal edge 227. Teeth 226 are contouredto mate with the multiplicity of divots disposed on an adjacent element.Accordingly, when overtube 22 is tensioned, retraction of tension wires36 (see FIG. 3) applies a clamping load to elements 30 that causes teeth226 of each element to forcefully engage divots 225 of an adjacentelement. This reduces the risk of relative angular movement betweenadjacent nestable elements 30 when overtube 22 is shape-locked, which inturn reduces the risk of undesired reconfiguration of the overtube.

To prevent divots 225 and teeth 226 from engaging, and thus providesmooth angular movement between adjacent elements 30, when overtube 22is in the flexible state, one or more leaf springs 228 may be moldedintegrally with proximal surface 32. Accordingly, absent compressiveclamping load applied by tension wires 36 to stiffen overtube 22, leafspring 228 of each element 30 coacts with distal surface 31 of anadjacent element to prevent coaction of proximal and distal surface 32and 31, which prevents engagement of teeth 226 with divots 225.

Alternatively, rather than having a leaf spring, nestable elements 30may be provided with one or more cantilever springs 229 that are cutfrom wall 34 and plastically bent into bore 33 of nestable element 30.Similar to leaf springs 228, cantilever springs 229 prevent coactionbetween distal and proximal surfaces 31 and 32 so that teeth 226 do notengage divots 225 absent a compressive clamping load. Cantilever springs229 may be aligned with a longitudinal axis of nestable element 30, asshown in FIG. 21B, and/or aligned with a circumference of nestableelement 30, as shown in FIG. 21C. Applicants also contemplate that teeth226 may be disposed on distal surface 31 and divots 225 may be disposedon proximal surface 32. One of ordinary skill in the art will recognizeadditional macroscopic textures that will increase friction betweendistal and proximal surfaces of adjacent elements 30.

On the other hand, instead of providing leaf or cantilever springsintegral with nestable elements 30, thin, flexible disc 232 (FIG. 21D)may be disposed between adjacent nestable elements 30 to prevent divots225 (see FIGS. 21A-21C) and teeth 226 of the adjacent elements fromengaging, absent a compressive clamping load. Each disc 232 incorporatescentral bore 233 that accommodates a colonoscope, and is made from anelastomeric material. For purposes of illustration, nestable elements 30and discs 232 are shown spaced-apart, but it should be understood thatthe elements and discs are disposed so that distal surface 31 of oneelement 30 and proximal surface 32 of an adjacent element coacts withdisc 232, which is disposed therebetween. It also should be understoodthat each nestable element 30 also comprises tension wire bores, whichare not shown in FIGS. 21A-21D for illustrative purposes.

Pursuant to one aspect of the present invention, nestable elements 30also may incorporate band 231 that is disposed distally adjacent toproximal edge 227. Band 231 increases the thickness of the proximalportion of wall 34 to distribute the applied compressive clamping loadover a larger cross-sectional area, and thereby reduce radially outwarddeflection of wall 34. This in turn reduces longitudinal contraction ofovertube 22. Band 231 preferably is made from a metal to provide greaterstructural integrity to wall 34, but also may be integral therewith.

In accordance with another aspect of the present invention, the diameterof lumen 25 preferably is configured to facilitate simultaneous passageof more than one diagnostic or therapeutic instrument therethrough. Asshown in FIG. 22, lumen 25 may be dimensioned to permit auxiliarydevices AD, such as for aspiration, biopsy, or additional lighting, tobe advanced alongside colonoscope 10. For example, if lumen 25 has adiameter of 13 mm and colonoscope 10 has an outer diameter of 10 mm,auxiliary device AD, such as a catheter, having a diameter of between 3F to 9 F may be advanced through the remaining space within lumen 25.Advantageously, this permits auxiliary devices AD to be successivelyplaced within the patient's colon to perform additional diagnostic ortherapeutic procedures without the need to remove colonoscope 10 andovertube 22 therefrom.

Referring to FIG. 23, an alternative embodiment of a distal regionsuitable for use in the overtube of the present invention is described.Distal region 235 is similar in construction to distal region 23 of theembodiment of FIG. 4, but has flexible coil 236 embedded in only theproximal portion of elastomeric layer 237. Atraumatic tip 238 at thedistal end of distal region 235 may further enhance the steerability ofovertube 22 when the steerable tip of the colonoscope is disposedtherein.

FIGS. 24-28 illustrate additional configurations of atraumatic tipssuitable for causing “tenting” of the wall of the hollow body organ. Asused herein, tenting refers to the tendency of the atraumatic tip to bedeflected radially outward in the vicinity of the tip of the overtube.This reduces the risk that the wall of the organ will become pinched orcaught between the colonoscope and the entry to overtube 22 when thecolonoscope is retracted within the overtube.

FIG. 24A shows atraumatic tip 24 in the form of an inflatabledonut-shaped balloon 240 affixed to distal region 23 of overtube 22.Inflation lumen 241 extends from the handle through overtube 22 toprovide fluid communication between balloon 240 and an inflation source,such as a syringe (not shown). As illustrated in FIG. 24B, when balloon240 is inflated, the wall of the colon radially deflects around balloon240. Thus, when colonoscope 10 is retracted into lumen 25, it is lesslikely that the wall of the colon will be pinched or potentiallydissected between overtube 22 and colonoscope 10. Furthermore, wheninflated, balloon 240 closes annular gap 242 disposed between the wallof overtube 22 and colonoscope 10 to prevent bodily fluids and othermatter from entering lumen 25. Advantageously, balloon 240 provides acustom fit around colonoscope 10.

FIG. 25 depicts a further alternative embodiment of atraumatic tip 24,comprising soft membrane 245 covering shape memory alloy petals 246.Petals 246 preferably comprise loops of shape memory alloy wire, e.g.,nickel titanium alloy, and extend radially outward in the proximaldirection near the distal opening into lumen 25, so that the proximalend of membrane-covered petals causes the “tenting” effect describedhereinabove. The shape memory alloy may be activated to adopt apre-formed shape when exposed to body temperature, and returned to acontracted state by flushing overtube 22 with cold water or air.Alternatively, petals 246 may be mechanically extended or retracted, orself-expanding.

FIG. 26 depicts a further alternative embodiment of atraumatic tip 24.In the embodiment of FIG. 26, petals 250 covered by soft elastomericmembrane 251 extend distally from distal region 23 to form funnel-shapedelement 252. Atraumatic tip 24 provides a similar tenting effect to thatdescribed for the preceding embodiments.

FIGS. 27-28 provide further alternative configurations for atraumatictip 86 of the embodiment of FIG. 9. Tip 255 preferably comprises a foamor soft elastomer, and may be affixed to distal region 23 of overtube 22using a suitable biocompatible adhesive. FIG. 28 depicts an alternativeshape for a foam or soft elastomer bumper 260, which includes aproximally-extending flange 261. Of course, one of ordinary skill in theart will recognize that other configurations may be used in accordancewith the principles of the present invention to form atraumatic tipsthat cause localized tenting of the colon wall, and these atraumatictips may be used with the passively-steerable distal regions of theembodiments of FIGS. 4 and 23.

Referring now to FIGS. 29 and 30, alternative embodiments of theovertube are described. Unlike overtube 22 of previously describedembodiments, in which a mechanical mechanism is actuated to impart aclamping load to a multiplicity of nestable elements, the embodiments ofFIGS. 29 and 30 use alternative tensioning mechanisms. In particular,the following embodiments comprise a multiplicity of links to which acompressive clamping load may be applied by contraction of shape memorymaterials.

In FIG. 29, a first alternative embodiment of the overtube of thepresent invention is described. Overtube 270 includes multiplicity ofnestable elements 30 identical to those described hereinabove. Forpurposes of illustration, nestable elements 30 are shown spaced-apart,but it should be understood that elements 30 are disposed so that distalsurface 31 of each element 30 coacts with proximal surface 32 of anadjacent element. Each of nestable elements 30 has central bore 33 toaccommodate colonoscope 10, and preferably two or more tension wirebores 35. When assembled as shown in FIG. 29, nestable elements 30 arefastened with distal and proximal surfaces 31 and 32 disposed in acoacting fashion by a plurality of tension wires 271 that extend throughtension wire bores 35.

In contrast to overtube 22 of the previous embodiments, tension wires271 of the present overtube are made from a shape memory material, e.g.,nickel titanium alloy or an electroactive polymer known in the art.Tension wires 271 are fixedly connected to the distal end of overtube270 at the distal ends and fixedly connected to handle 21 at theproximal ends. When an electric current is passed through tension wires271, the wires contract in length, imposing a compressive clamping loadthat clamps distal and proximal surfaces 31 and 32 of nestable elements30 together at the current relative orientation, thereby fixing theshape of overtube 270. When application of electrical energy ceases,tension wires 271 re-elongates in length to provide for relative angularmovement between nestable elements 30. This in turn renders overtube 270sufficiently flexible to negotiate a tortuous path through the colon.

To provide overtube 270 with a fail-safe mode that reduces the risk ofundesired reconfiguration of the overtube in the event of tensioningmechanism failure, diametrically disposed tension wires 271 may becoupled in a serial circuit. Accordingly, when one wire fails, the wiredisposed diametrically opposite also re-elongates to maintain asymmetrical clamping load within overtube 270. Alternatively, alltension wires 271 may be electrically coupled in a serial electricalcircuit. Accordingly, when one of the tension wires fails, overtube 270returns to the flexible state.

It should be understood that a tension spring (not shown) or damper (notshown) that are similar to those described hereinabove may be coupledbetween the proximal ends of tension wires 271 and handle 21 (see FIG.2). Inter alia, this maintains the tension wires in constant tensionwhen the overtube is in the shape-locked state, thereby reducing therisk of reconfiguration of the overtube to its flexible state ifnestable elements disposed therein slightly shift relative to adjacentnestable elements.

Alternatively, as described in FIG. 30, overtube 280 may includemultiplicity of nestable elements 281 that are similar to those of thepreceding embodiments. For purposes of illustration, nestable elements281 are shown spaced-apart, but it should be understood that elements281 are disposed so that distal surface 282 of each element 280 coactswith proximal surface 283 of an adjacent element. Each of nestableelements 280 has central bore 284 to accommodate colonoscope 10.

When assembled as shown in FIG. 30, nestable elements 280 are fastenedwith distal and proximal surfaces 282 and 283 disposed in coactingfashion by plurality of thin tension ribbons 285 that are fixedlyconnected to nestable bridge elements 286. Tension ribbons 285 are madefrom a shape memory material, e.g., nickel titanium alloy or anelectroactive polymer, and may be transitioned from an equilibriumlength to a contracted length when electrical current is passedtherethrough.

Nestable bridge elements 286 are disposed within overtube 280 between apredetermined number of nestable elements 281. Similar to nestableelements 281, bridge elements 286 also comprise central bore 287 thataccommodates colonoscope 10, distal surface 288 that coacts withproximal surface 283 of a distally adjacent nestable element, andproximal surface 289 that coacts with distal surface 282 of a proximallyadjacent nestable element 281. Each bridge element also incorporatesplurality of conductive elements 290 that are disposed azimuthallyaround central bore 287, and that preferably couple tension ribbons 285occupying the same angular circumferential position within overtube 280in a serial electrical circuit.

When an electrical current is passed through tension ribbons 285, theribbons contract in length, imposing a compressive load that clampsdistal and proximal surfaces of adjacent nestable elements together atthe current relative orientation, thereby fixing the shape of overtube280. When the energy source ceases providing electricity, tensionribbons 285 re-elongates to the equilibrium length to provide forrelative angular movement between the nestable elements. This in turnrenders overtube 280 sufficiently flexible to negotiate a tortuous paththrough the colon.

Pursuant to another aspect of the present invention, tension ribbons 285that are disposed at diametrically opposite circumferential positionsmay be electrically coupled in a serial circuit. Advantageously, thisconfiguration provides overtube 280 with a fail-safe mode that reducesthe risk of undesired reconfiguration of the overtube in the event thatone of the electrical circuits established through the tension ribbonsis de-energized.

For example, overtube 280 of FIG. 30 may be provided with four sets oftension ribbons equidistantly disposed at 90° intervals. In the eventthat tension ribbons T_(a) de-energize, absent electrical communicationbetween tension ribbons T_(a) and tension ribbons T_(c) disposeddiametrically opposite thereto, overtube 280 will spontaneouslyreconfigure into a new rigidized shape since the tension within theovertube no longer will be symmetrically balanced. The new shape ofovertube 280 may not replicate the tortuous path of the colon, and thusmay cause substantial harm to the patient.

Advantageously, the present invention may reduce the risk of undesiredreconfiguration preferably by electrically coupling diametricallydisposed tension ribbons in a serial circuit. When tension ribbons T_(a)are de-energized, tension ribbons T_(c) also de-energize to provideovertube 280 with symmetrical tension, as provided by tension wiresT_(b) and the tension wires disposed diametrically opposite thereto (notshown). In this manner, the overtube retains its desired rigidized shapein the event that the tensioning mechanism malfunctions. To immediatelyreturn overtube 280 to its flexible state in the event that any of thetension ribbons are de-energized, all tension ribbons 285 may beelectrically coupled in a serial circuit.

In an alternative embodiment, tension ribbons 285 may be electricallycoupled to rigidize select regions of the overtube without rigidizingthe remainder of the overtube. Illustratively, this may be accomplishedby coupling longitudinally adjacent tension ribbons in a parallelcircuit, and circumferentially adjacent tension ribbons in a serialcircuit.

Of course, it will be evident to one of ordinary skill in the art that,while FIG. 30 depicts tension ribbons 285 to be disposed within centralbores 284 and 287, the tension ribbons also may be disposed adjacentexternal lateral surfaces 292 of nestable elements 281 and 286.Alternatively, the tension ribbons may extend through tension ribbonbores (not shown) that may extend through the distal and proximalsurfaces of nestable elements 281, and be affixed to nestable bridgeelements 286.

With respect to FIGS. 31-37, alternative embodiments of overtube 22 aredescribed. Unlike overtube 22 of the above-described embodiments, whichcomprised a multiplicity of nestable elements that are clamped with aplurality of tension wires or ribbons, the embodiments of FIGS. 31-37use alternative clamping mechanisms. In particular, the followingembodiments comprise a plurality of links that may be stiffened by theuse of compressive sleeves that compress individual links disposed alongthe length of the overtube.

Referring now to FIGS. 31A-31C, a fourth alternative embodiment of theovertube of the present invention is described. Overtube 300 comprises amultiplicity of alternating spool links 301 and clamp links 302. Eachspool link 301 and clamp link 302 has a bore disposed therethrough toaccommodate a standard colonoscope. Spool link 301 comprises roundededges 303 disposed on its distal and proximal ends that are contoured topermit limited rotatable engagement with one of two contoured grooves304 disposed within the bore of clamp link 302. Accordingly, clamp link302 comprises a greater outer diameter than spool link 301. Each clamplink 302 also has through-wall split 305 longitudinally disposed topermit a reduction in the diameter of clamp link 302 when the clamp linkis compressed, as discussed hereinafter.

Still referring to FIGS. 31A-31C, a first embodiment of a compressivesleeve comprising inflatable sleeve 310 having first compressiveportions 311 and second compressive portions 312. Sleeve 310 isconfigured so that the inner diameters of second compressive portions312 are smaller than those of first compressive portions 311 when sleeve310 is inflated. Second compressive portions 312 may be disposed toengage clamp links 302. Thus, when inflatable sleeve 310 is inflated byan inflation source (not shown) coupled to the handle, secondcompressive portions 312 compress against clamp links 202 to shape-fixovertube 300. In FIGS. 31B and 31C, cross sectional views of firstcompressive portions 311 and second compressive portions 312,respectively, are shown when sleeve 310 is in its inflated state.

FIG. 32 illustrates an alternative embodiment of a compressive sleevethat also comprises an inflatable bladder. Unlike inflatable bladder 310of FIGS. 31A-31C, spiral bladder 320 has a constant inner diameter.Spiral bladder 320 preferably is helically disposed around the overtube.Accordingly, when bladder 320 is inflated, clamp links 302 arecompressed onto spool links 301 to stiffen the overtube.

FIG. 33 depicts a further embodiment of a compressive sleeve 330,comprising discontinuous hoops 331 made of shape memory alloy (e.g.nickel titanium alloy). Each hoop 331 includes gap 332, which is spannedby spring 333. Each hoop 331 is electrically connected to neighboringhoops 331 via insulated wires 334, so that a serial electrical circuitis established. When hoops 331 are energized, they undergo a phasetransition that causes the hoops to contract into a preformed shape thatis diametrically smaller than the non-energized shape. Since hoops 331may be disposed about clamp links 302, contraction of hoops 331 may beused to apply a clamping load that compresses links 302 onto spool links301 to stiffen the overtube.

Springs 333 contribute to structural integrity when hoops 331 are intheir non-energized state. To energize and thereby contract hoops 331,an electrical current may be run through wires 334. To return hoops 331to their non-contracted state and thereby return the overtube to itsflexible state, hoops 331 may be flushed with cold water or air. Ofcourse one of ordinary skill in the art will recognize that hoops 331also may be individually energized, thus requiring a parallel circuit.

With respect to FIGS. 34A-34B, a still further alternative embodiment ofan overtube suitable for use in the present invention is described. Thisembodiment comprises helical links 340 that are formed from an integralstrip 341 having regions of different durometer, e.g., rigid material342 and soft material 343. When strip 341 is helically wound, helicallinks 340 are formed having rigid portions 344 and soft portions 345.Rigid portions 344 provide structural integrity to the overtube, whilesoft portions 345 provide flexibility.

Helical links 340 are disposed within compressive sleeve 346, whichincludes first compressive portions 347 and second compressive portions348. Compressive sleeve 346 is identical in structure and operation tothat described in FIGS. 31A-31C, except that second compressive portions348 are aligned with, and apply a clamping force to, rigid portions 344of helical links 340. It will of course be understood that an overtubein accordance with the principles of the present invention couldalternatively be formed using helical links 340 and either of theclamping systems described with respect to FIGS. 32 and 33.

Referring now to FIG. 35, another alternative embodiment of an overtubeis described, in which each Grecian link 350 includes rigid first andsecond rims 351 and 352 disposed at longitudinally opposing ends offlexible body 353. First rim 351 comprises U-shaped arm 354 that defineschannel 355 and opening 356. Second rim 352 includes retroflexed arm357, which when engaged to first rim 351 of an adjacent, is disposedwithin channel 355 of U-shaped arm 354 through opening 356 so thatU-shaped arm 354 and retroflexed arm 357 are engaged and overlap alongthe longitudinal axis of the overtube.

Grecian links 350 are disposed within compressive sleeve 358, whichincludes first compressive portions 359 and second compressive portions360. Compressive sleeve 358 is identical in structure and operation tothat described in FIGS. 31A and 34A, except that second compressiveportions 360 are aligned with, and apply a clamping force to,overlapping U-shaped arm 354 and retroflexed arm 357 of the first andsecond rims. It will of course be understood that an overtube inaccordance with the principles of the present invention couplealternatively be formed using Grecian links 350 and either of theclamping systems described with respect to FIGS. 32 and 33.

Referring now to FIG. 36, yet another alternative embodiment of anovertube suitable for use in the present invention is described. Thisembodiment comprises joint links 370 that include ball 371 and socket372 disposed at longitudinally opposing ends of flexible body 373. Whenadjacent joint links 370 are engaged, ball 371 of one link is disposedwithin socket 372 of an adjacent link. When the overtube is flexed, ball371 coacts with socket 372 to provide articulation of the overtube.

Joint links 370 are disposed within compressive sleeve 374, whichincludes first compressive portions 375 and second compressive portions376. Compressive sleeve 374 is identical in structure and operation tothat described in FIGS. 31A, 34A and 35, except that second compressiveportions 376 are aligned with, and apply a clamping force to, socket 372within which ball 371 of an adjacent link is disposed. It will of coursebe understood that an overtube in accordance with the principles of thepresent invention couple alternatively be formed using joint links 370and either of the clamping systems described with respect to FIGS. 32and 33.

With respect to FIG. 37, a still further embodiment of an overtubesuitable for use in the apparatus of the present invention is described.Overtube 380 comprises a heat-softenable polymer layer 381, (e.g.,Carbothane®, a proprietary urethane-based polymer available fromThermedics Polymer Products, Woburn, Mass.), having wire 382 embeddedwithin it. Wire 382 is coupled at the handle to an energy source, sothat by passing an electric current through wire 382, sufficientresistive heating occurs to soften the polymer layer 381, rendering itsufficiently flexible to negotiate tortuous or unsupported anatomy. Whenelectrical energy is not supplied to wire 382, no resistive heating ofthe wire or the polymer layer occurs, and the overtube instead cools andstiffens. Wire 382 serves the dual purpose of providing kink resistanceand electric heating.

Still referring to FIG. 37, yet another alternative embodiment of anovertube suitable for use in the present invention comprises a softelastomeric polymer layer 381 having a shape memory alloy wire 382embedded within layer 381. In this embodiment, the shape memory alloy isselected to have a martensite transition temperature above bodytemperature. When wire 382 is heated to a temperature above bodytemperature, such as by passing an electric current through it, the wiretransitions into the austenitic phase, and becomes stiffer, therebyshape locking the overtube. When application of the electric currentceases, wire 382 cools back into the martensitic phase, and renders theovertube flexible.

Referring now to FIGS. 38A-38C, an additional alternative embodiment ofan overtube suitable for use with the present invention is described.Overtube 390 comprises elongate body 391 having central lumen 392 thataccommodates colonoscope 10, and wire lumens 393 that are defined bycylindrical wire lumen surfaces 394. Within each wire lumen 393 isdisposed wire 395 that extends the length of the elongate body. Elongatebody 391 is made from an electroactive polymer known in the art thatpermits wire lumens 393 to vary in diameter responsive to electricalenergization.

In particular, when an electrical current is passed through elongatebody 391, the diameter of each wire lumen 393 decreases so that the wirelumens clamp around respective wires 395. Preferably, both wires 395 andwire lumen surfaces 394 are textured to enhance friction therebetween.This prevents further relative movement between elongate body 391 andwires 395, and stiffens overtube 390. When application of the electricalcurrent ceases, wire lumens 393 increase in diameter to release wires395 so that elongate body 391 may shift relative to wires 395. This inturn renders overtube 390 sufficiently flexible to negotiate a tortuouspath through the colon.

With respect to FIG. 39, yet another alternative embodiment of theovertube is described. Overtube 400 incorporates multiplicity ofvariable diameter links 401 disposed in overlapping fashion surroundingmultiplicity of rigid links 402, that provide structural integrity tothe overtube. Each link comprises a central bore that defines lumen 25of the overtube, and accommodates a standard commercially availablecolonoscope. Variable diameter links 401 preferably are manufacturedfrom an electroactive polymer or a shape memory alloy that contract indiameter when energized. When variable diameter links 401 areelectrically activated, the variable diameter links tighten about rigidlinks 402 to transition overtube 400 into a shape-locked state. When thevariable diameter links are electrically deactivated, the variablediameter links sufficiently soften to return overtube 400 back to theflexible state.

In a preferred embodiment, variable diameter links 401 and rigid links402 are formed from respective strips of material that are helicallywound in an overlapping fashion to form overtube 400. Alternatively,each link may be individually formed and disposed in an overlappingfashion.

In FIGS. 40A-40B, still another alternative embodiment of an overtubesuitable for use with the apparatus of the present invention isillustrated schematically. Overtube 405 comprises multiplicity ofnestable hourglass elements 406 that preferably are manufactured from anelectroactive polymer or a shape memory alloy, and each have bulbousdistal and proximal portions 407 and 408 connected by neck 409. Thediameter of neck 409 is smaller than the maximum diameter of distalportion 407, which in turn is less than the maximum diameter of proximalportion 408. The distal portion of external surface 410 of eachhourglass element 406 is contoured to coact with the proximal portion ofinternal surface 411 of a distally adjacent hourglass element.Accordingly, when a multiplicity of hourglass elements are nestedtogether to form overtube 405, adjacent elements 406 may move relativeto each other when the overtube is in the flexible state.

To reduce friction between adjacent elements during relative movementtherebetween, proximal portions 408 include plurality of slits 412disposed contiguous with proximal edge 413. Slits 412 also facilitatecontraction of proximal portion 408 of each element around distalportion 407 of an adjacent element. Each hourglass element 406 also hascentral bore 414 that accommodates colonoscope 10 (see FIG. 1).

When an electrical current is applied to multiplicity of nestablehourglass elements 406, proximal portion 408 of each element contractsin diameter around distal portion 407 of an adjacent element. Thecompressive clamping force thereapplied prevents relative movementbetween adjacent elements, thereby shape-locking the overtube. When thenestable elements are de-energized, proximal portions 408 sufficientlyrelax to permit relative movement between adjacent nestable elements406, and thus permit overtube 405 to negotiate tortuous curves. Forpurposes of illustration, it should be understood that the figures ofthe present application may not depict an electrolytic medium,electrodes, and insulated wires that are coupled to and facilitateionization, and thus contraction, of the electroactive polymersdescribed herein.

In accordance with another aspect of the present invention, the overtubeof the present invention may be provided with disposable sheath 420 thatmay extend the length of overtube 22 and be removed therefrom. Like thesheath described hereinabove with respect to FIG. 4, sheath 420 of FIG.41 also incorporates distally-disposed atraumatic tip 421 and flexible,kink-resistant coil 422 encapsulated in flexible layer 423. At itsproximal end, layer 423 joins or is integrally formed with lubriciousliner 424 defining lumen 425, and flexible elastomeric skin 427. Liner424 may incorporate optional flexible, kink-resistant coil 429, be madeof a thin, flexible material, and/or have a hydrophilic coating thereon,similar to that described in reference to FIG. 4. Between liner 424 andskin 427 is disposed annular chamber 428 within which nestable elements30 may be inserted. Sheath 420 is configured to slide onto and beremoved from a column of nestable elements 30 so that the sheath may bediscarded after a single use, while the nestable elements and handle maybe sterilized and reused. Advantageously, substantial cost reductionsmay be realized.

Pursuant to another aspect of the present invention, apparatus 20further may be provided with a device to secure colonoscope 10 toapparatus 20 prior to insertion of apparatus 20 and colonoscope 10 intothe patient. FIG. 42 depicts strap 430 that may be secured distally tohandle 21 of apparatus 20 and proximally to proximal portion 13 ofcolonoscope 10. Strap 430 preferably has a length that preventscolonoscope 10 from decoupling from apparatus 20 after the colonoscopeis placed within the overtube. Illustratively, strap 430 may be made ofductile wire or Velcro. If strap 430 is made of ductile wire, the strapmay be secured to anchors 431 and 432 respectively disposed on handle 21and colonoscope 10. Anchor 432 may be integral with, or comprise anadhesive suitable for application to colonoscope 10.

Referring now to FIG. 43, a loading device for inserting a liner withinapparatus of the present invention is described. In FIG. 43, apparatus500 comprises rigidizable/shape-lockable overtube 510, which is coupledto handle 520. Sheath 512 is disposed about the exterior of overtube510, and lumen 511 extends through the overtube and handle 520. Overtube510 and handle 520 may, for example, be similar to any handle orovertube described previously hereinabove.

FIG. 43 illustrate apparatus and methods for disposing liner 550, whichmay comprise a hydrophilic liner and/or may be similar to previouslydescribed liner 43 or previously described liner 424, within lumen 511of apparatus 500. Liner 550 is coupled to a distal end of loading device560, which illustratively comprises elongate tube or rod 562. Rod 562preferably is more rigid than liner 550 in order to facilitate placementof the liner.

Liner 550 may be inserted within lumen 511 of apparatus 500 by pushing aproximal end of rod 562 through a distal end (not shown) of overtube 510and lumen 511. Continued advancement of rod 562 through lumen 511 causesthe rod to exit the lumen through proximal handle 520. The rod then maybe pulled more proximally until liner 550 exits lumen 511, as seen inFIG. 43. Once inserted within the lumen, liner 550 may be decoupled fromloading device 560, for example, by cutting the liner at a positionbetween the proximal end of handle 520 and the distal end of rod 562.

Sheath 512 optionally may be distally coupled to liner 550, andoptionally may be advanced over the exterior of overtube 510 concurrentwith the advancement of liner 550 through lumen 511. In such aconfiguration, loading device 560 is utilized to properly position bothexternal sheath 512 and internal liner 550 about apparatus 500. Thesheath and liner may, for example, be disposable and facilitate re-useof overtube 510 and handle 520.

Referring now to FIG. 44, an alternative loading device, liner andapparatus handle are described. Alternative handle 520′ of apparatus 500comprises anchor post 522. Alternative loading device 560′ comprises rodor tube 562′ having alignment indicator 564. Alternative liner 550′comprises detachment perforation 552, anchoring hole 554 and access slit556.

Slit 556 distally terminates at strain relief 557, which reduces a riskof slit 556 propagating distally along the length of liner 550′.Alignment indicator 564 of rod 562′ preferably is aligned with slit 556to facilitate proper orientation of liner 550′ within apparatus 500, andmore specifically within handle 520. As discussed hereinafter, anchoringhole 554 of liner 550′ preferably is aligned with anchoring post 522 ofhandle 520′ for securing the liner to the handle.

Liner 550′ may be disposed within lumen 511 of apparatus 500 in a mannersimilar to that described previously with respect to liner 550 of FIG.43. The liner may be inserted within the lumen by pushing a proximal endof rod 562′ through a distal end of overtube 510 and lumen 511 until therod exits the lumen through handle 520′. The rod then may be pulled moreproximally until liner 550′ exits the lumen, as in FIG. 44. Preferably,alignment indicator 564 is utilized while proximally pulling rod 562′ inorder to properly align liner 550′ with apparatus 500 and handle 520′.

Referring now to FIG. 45, a method of detaching loading device 560′ fromliner 550′ is described. Liner 550′ may be torn at perforation 552 todetach the liner from the loading device. Advantageously, detachmentperforation 552 allows a medical practitioner to separate the liner fromthe loading device without requiring additional cutting tools.

With reference to FIG. 46, an illustrative method of securing liner 550′to handle 520′ of apparatus 500 is described. As discussed previously,anchoring hole 554 of the liner preferably is aligned with anchor post522 of the handle, e.g. via alignment indicator 564 of loading device560′. Once liner 550′ has been separated from loading device 560′ atperforation 552, slit 556 of the liner may be manipulated such thatanchoring hole 554 of the liner is distended about anchor post 522 ofthe handle. In this manner, liner 550′ is reversibly coupled to thehandle, thereby reducing a risk of the liner migrating distally withinapparatus 500 during advancement of an endoscope or other instrument(s)through lumen 511 of the apparatus. Additional and/or alternativemethods and apparatus for securing liner 550′ to handle 520′ will beapparent to those of skill in the art.

In addition to facilitating coupling of the liner to the handle, slit556 of liner 550′ provides multiple benefits. The slit expands theproximal end of the liner, which facilitates access to lumen 511 ofapparatus 500 through the liner. Additionally, the expanded liner actsas a buffer between handle 520′ and an endoscope or other instrument(s)advanced through the handle, thereby protecting the scope/instrument(s)from damage during advancement through the handle. The expanded lineralso reduces contact surface area at the mouth of handle 520′, therebysimplifying scope/instrument handling. Furthermore, the expanded linerprovides funnel-like access to liner 550′, which facilitates wettingand/or rewetting of the liner. Advantageously, such wetting may beachieved with a standard syringe, as opposed to a specialized irrigator.

Referring now to FIG. 47, a variation of the apparatus of FIG. 46 isdescribed comprising a fluid reservoir. Fluid reservoir 600 preferablyis coupled to handle 520′, but may be positioned at alternativelocations. Reservoir 600 illustratively comprises tubing 602, whichcommunicates with lumen 511. Fluids may be deposited within lumen 511and/or along the shaft of an endoscope or instrument(s) disposed withinthe lumen, by dispensing fluid from reservoir 600. Exemplary fluidsinclude, but are not limited to, wetting fluids, water, lubricants,hydrophilic fluids and combination thereof.

It will be obvious to one of ordinary skill in the art that, while theabove description has emphasized use of apparatus of the presentinvention in the lower gastro-intestinal tract, and in particular, inperforming colonoscopy, the apparatus of the present invention also maybe used in the upper gastro-intestinal tract, and in laparoscopicprocedures as a variable rigidity trocar through which a steerablelaparoscopic endoscope or tool may be advanced. Apparatus describedherein also may be scaled down in size for use in endo-urologicalprocedures. For example, a miniaturized overtube may be advanced, alongwith a steerable nephrescope, through a patient's ureter into a kidneyfor access to the kidney's lower pole.

While preferred illustrative embodiments of the invention are describedabove, it will be apparent to one skilled in the art that variouschanges and modifications may be made therein without departing from theinvention. The appended claims are intended to cover all such changesand modifications that fall within the true spirit and scope of theinvention.

1. Apparatus for advancing a first diagnostic or therapeutic instrumentinto a hollow body organ of unsupported anatomy, the apparatuscomprising: a handle; an overtube having a proximal end and a distalend, with the proximal end being coupled to the handle, the overtubehaving a lumen to permit passage of a first diagnostic or therapeuticinstrument; a liner for the lumen of the overtube, the liner having aproximal end and a distal end and having a length that is substantiallyequal to or greater than a length of the overtube; and a loading devicefor disposing the liner within the lumen of the overtube, the loadingdevice comprising an elongate member having a proximal end and a distalend with the distal end of the loading device being reversibly coupledto the proximal end of the liner, the elongate member having a size andshape to allow the elongate member to be inserted proximal end firstinto the lumen at the distal end of the overtube, advanced through thelumen, and exit the lumen at the proximal end of the overtube such thatthe distal end of the elongate member and the proximal end of the linerexit the lumen at the proximal end of the overtube.
 2. The apparatus ofclaim 1, wherein the liner is configured to provide a barrier betweenthe interior surface of the overtube and the first diagnostic ortherapeutic instrument.
 3. The apparatus of claim 2, wherein the linercomprises an inner portion of a sheath defining an annular chamberconfigured to accept the overtube, the liner forming an inner portion ofthe sheath, an outer portion of the sheath configured to cover anexterior surface of the overtube.
 4. The apparatus of claim 3, whereinthe loading device is configured to dispose the overtube within theannular chamber.
 5. The apparatus of claim 3, wherein the sheath isdisposable.
 6. The apparatus of claim 3, wherein the sheath comprises ahydrophilic material.
 7. The apparatus of claim 3, wherein the sheathcomprises a non-kinking coil.
 8. The apparatus of claim 2, wherein theovertube comprises a plurality of nestable links that each has a lateralwall.
 9. The apparatus of claim 8, further comprising: a plurality oftension wire bores extending through the lateral wall of each one of theplurality of nestable links; and at least one tension wire translatablydisposed through one or more of the plurality of tension wire bores. 10.The apparatus of claim 1, wherein the overtube further comprises aflexible state that facilitates insertion of the overtube into a hollowbody organ, and a rigid state wherein the overtube resists bendingforces exerted on the interior surface during insertion or withdrawal ofthe first diagnostic or therapeutic instrument though the lumen.
 11. Theapparatus of claim 8, wherein the overtube further comprises a flexiblestate that facilitates insertion of the overtube into a hollow bodyorgan, and a rigid state wherein the overtube resists bending forcesexerted on the interior surface during insertion or withdrawal of thefirst diagnostic or therapeutic instrument though the lumen.
 12. Theapparatus of claim 11, further comprising a tensioning mechanismselectively operable to transition the overtube between the flexible andrigid states.
 13. The apparatus of claim 12, wherein the tensioningmechanism comprises a plurality of tension wires that threads theplurality of nested links together.
 14. The apparatus of claim 12,wherein the tensioning mechanism is configured to apply adistally-directed clamping load to the plurality of nestable links. 15.The apparatus of claim 1, wherein the elongated member comprises analignment indicator for properly aligning the liner within the lumen ofthe overtube.
 16. The apparatus of claim 1, wherein the liner comprisesa perforation for separating the liner from the elongated member. 17.The apparatus of claim 1, wherein the liner comprises an expandableproximal region.
 18. The apparatus of claim 1, further comprising afluid reservoir adapted for delivery of fluid to the lumen of theovertube.
 19. A method of disposing a liner within apparatus foradvancing a first diagnostic or therapeutic instrument into a hollowbody organ of unsupported anatomy, the method comprising: reversiblycoupling a proximal end of the liner to a distal end of a loadingdevice; inserting a proximal end of the loading device into a lumenopening at a distal end of the apparatus; advancing the loading devicethrough the lumen of the apparatus; and decoupling the liner from theloading device.
 20. The method of claim 19, further comprising disposingthe apparatus within an annular chamber formed by a sheath, the linerforming an inner portion of the sheath.
 21. The method of claim 19,wherein decoupling the liner from the loading device further comprisestearing the liner along a perforation.
 22. The method of claim 19,further comprising securing the liner to the apparatus.
 23. The methodof claim 19, further comprising expanding a proximal region of theliner.
 24. Apparatus for disposing a liner within a lumen of an overtubethat is configured for advancing a first diagnostic or therapeuticinstrument into a hollow body organ of unsupported anatomy, theapparatus comprising: a loading device reversibly coupled to the liner,the liner having a proximal end and a distal end and having a lengththat is substantially equal to or greater than a length of the overtube,the loading device comprising an elongated member configured foradvancement through the lumen of the overtube, the elongated memberhaving a proximal end and a distal end with the distal end beingreversibly coupled to the proximal end of the liner, the elongatedmember having a size and shape to allow the elongated member to beinserted proximal end first into the lumen at a distal end of theovertube, advanced through the lumen, and exit the lumen at a proximalend of the overtube such that the distal end of the elongated member andthe proximal end of the liner exit the lumen at the proximal end of theovertube; and a perforation along the liner for separating the linerfrom the loading device.
 25. The apparatus of claim 24, wherein theliner comprises an expandable proximal region.
 26. The apparatus ofclaim 24, wherein the liner is configured for reversible coupling to theovertube after separation of the liner from the loading device.